Apparatus for the heat treatment of running yarns



Jan. 9, 1962 c. R. JoNEs 3,015,872

APPARATUS FOR THE HEAT TREATMENT OF RUNNING YARNS Filed April 15, 1958Inventor C'L/ve F/G/fro/v Q/o/vgs Attorneys @taies 3,015,872 PatentedJan. 9, 1962 3,015,872 APPARATUS EUR THE HEAT TREATMENT F RUNNING YARNSClive Righten Jones, Ahergavenny, England, assigner to British NylonSpinners Limited, Monmouthshire, England Filed Apr. 15, 1953, Ser. No.728,635 Claims priority, application Great Britain Apr. 25, 1957 2Claims. (Cl. 28-62) The present invention relates to a process andapparatus for the heat treatment of running yarns, and has particularthough not exclusive reference to such a treatment with dry heat. Theterm ya-rn is herein used in the specication and claims to indicatesingle or multiiilament structures; and includes cords, whether singleor plied, and whether as single ends o-r in the form of a Warp fabric,such as tyre-cord fabric.

It is often required to submit a running yarn or a plurality of suchyarns to a heat treatment, as for example during stretching undertension, or during crimping processes such as those depending ondeformation of the synthetic yarns by false-twisting or by passage ofthe yarns while hot over an edge. The etliciency of the heatingapparatus may well be the governing factor in the productivity of theprocess concerned, as considerations of space will often prevent theheating apparatus from being more than, at the most, a few feet long,and this will limit the speed at which the yarn or yarns may be passedthrough the heater so that the heat treatment may be effective.

Various types of heating apparatus are known for the heat treatment ofsynthetic yarns, such as nylon yarns, some depending on conduction andsome on radiation and convection to effect the transfer of heat `fromthe heating element to the yarn. One of the simpler forms ofheatconduction apparatus is a curved heated-plate with which the yarnmakes a suitable line contact, but this apparatus has the disadvantagethat, as the heat is applied to one side of the yarn only, the averageyarn temperature must always be lower than that plate surfacetemperature at which the laments of the yarn in contact with the pl-atewould melt or be degraded. Thus, for any particular yarn there is laclearly defined maximum temperature above which it is not safe tooperate and the only way of increasing the ecacy of the apparatus is byincreasingthe length of the line of contact with the yarn, which, asalready stated, is usually prohibited by considerations ofrspace. Asimple form of radiation apparatus comprises an airlled metal tubethrough the middle of which the yarn passes, the walls of the tube being4heated by electric heating coils wrapped around them. This type ofapparatus has advantages over the contact type in that all sides of theyarn can be heated simultaneously to the same amount, and in that thetemperature of the heating elements can be raised well above the melting(or degrading) temperature of the yarn, at high yarn speeds, withoutdamaging the yarn.

What is required of any heat treatment apparatus is that it should heatthe yarn up to the required temperature and hold it at that temperature`for a time suicient to achieve the purpose of the treatment, e.g. thesetting of the yarn if it is a yarn such as nylon which has the abilityto be permanently set by hea-t in the configuration adopted by it at thetime of the heat treatment. What the temperature and the time shall bein any given instance will depend on the nature of the treatment, thekind of yarn and its diameter, and the type of heating apparatus, but inevery instance there will be some finite time (and correspondingdistance) during which some or all parts of each successive length ofthe yarn passing through or in contact with the heater will be rising intemperature towards the desired, or equilibrium, temperature.

so that the yarn may be processed at greater linear speedsy for a givenlength of heater,

It is another object of the invention to provide a yarn heatingapparatus having a plurality of heating zones in each of which thetemperature distribution is substantially uniform throughout the greaterpart of the zone.

The present invention in one aspect comprises a process for the heattreatment of running yarns, especially continuous iila'ment yarns ofsynthetic thermoplastic materials, wherein yarn is drawn through aheating jacket and successive lengths of the yarn `a-re thereinsubjected lirstly to heat at a temperature considerably in excess of thetreatment equilibrium temperature for -a time suicient to raise thetemperature of the yarn substantially to the said equilibriumtemperature but insuicient to damage or degrade the material of theyarn, and secondly to heat at the equilibrium temperature for a timesuicient to achieve the purpose of the treatment. The invention inanother aspect comprises apparatus for the heat treatment of runningyarns, especially continuous filament yar-ns of synthetic thermoplasticmaterials, drawn therethrough comprising a thermally-insulated heatingjacket having a distinct pre-heating zone and a distinct equilibriumheating zone, and having means to supply heat to the said preheatingZone land means to supply heat to the said equilibrium Zone, the`first-mentioned means being adapted to supply heat ata highertemperature than the second-mentioned means.

In order that 4the nature of the invention may become v apparent therewill now be described, with reference to the accompanying drawings, oneconvenient apparatus, together with its mode of use, provided by andillustrative of the invention.

In the accompanying drawings:

FIGURE l is a longitudinal section of the said apparatus through theline C-C of FIGURE 2 or 3;

FIGURE 2 is a section rotated 90 clockwise through the line A-A o-fFIGURE l; and

FIGURE 3 is a section rotated 90 clockwise through the line B-B ofFIGURE 1.

The apparatus essentially comprises a heating jacket 1 of rectangularcross-section some two feet in length, through a lcentral space in whichtwo yarns 3, 5 are passed, travelling in the direction from top tobottom of the jacket. The yarns, after attaining full running speed, areinsertedY into operative position within the jacket by means of aclosure member 7, shown diagrammatically in FIG- URE 1, which carriesyarn-guides 9, 11 and 13, 15 on its l upper land lower extremitiesrespectively. As shown by the chain-dotted and the solid lines depictingmember 7 in two positions, the member is capable of lateral movement soas to be able to move the yarns through a longitudinal threading slot 17into and out of operative position Within the jacket, as it is notdesired to insert the yarns until they are moving at operating speed,owing to the very high temperature of the apparatus. The jacketcomprises an aluminium casing 19 dening within it two district,contiguous thermally-insulated heating zones 21, 23, of which the former(pre-heating) zone 21 is at a considerably higher temperature than thelatter (equilibrium) zone 23. The heating elements of both Zones arethermally insulated from the casing 19 by solid insulating material 25;and both ends of the jacket are thermally insulated from the atmosphereby blocks of solid insulating material 27, 29. The two zones arethermally insulated from each other by an air-space 31 of some 1A; inchthickness between the metal end-plates of the two heatingzones.

As shown in FIGURES l and 2, the part of the apparatus defining thepre-heating zone 21 has an interconnected double J -shaped electricalheating element 33, each leg of which is brazed to a brass block 35 ofU-shaped horizontal section. The element comprises an electricalresistance wire packed in a refractory insulating material inside astainless steel tube and is adapted to produce a treatment temperatureof, say, 460 C. Yarns 3, 5 run within the central air-lled space,comprising the pre-heating zone 2i, between the legs of the element 33and are heated by radiation and by the hot air therein. As can be seenfrom FIGURE 2, the threading slot i7 tapers inwardly to an inside widthof 1A@ inch, and the member 7 is actually shaped to fit closely withinthe outer part of the slot so as to complete the thermal insulation ofthis side of the jacket when the yarns are in operating position withinit. The entrance to the narrow part of the slot is defined by two solidblocks of insulating material 39, 41. The slot is also formed throughend-block 27, as shown at 37 in FIGURE 2, and end-block 29. It ispreferable if there is an air-gap of some 1/s inch Width between theoutside of blocks 39, 41 and the inside of member 7 when the latter isin the closed position, in order that the effect on the temperature ofthe yarn spaces within the heater of removing mem-ber 7 from the outerpart of the slot shall not be too pronounced and in order that thetemperature shall rise quickly and directly to the operating temperaturewhen the yarns are inserted.

As shown in FIGURES l and 3, the part of the apparatus defining theequilibrium heating zone 23 has two parallel metal elements 43, 45, someMr inch thick and each containing an electric resistance wire packed ina refractory insulating material and each flanked on both sides by brassplates 47, 49 and 51, 53 respectively. The elements are adapted toproduce a treatment temperature of, say 260 C. Yarns 3, 5 run in theair-filled space comprising the equilibrium heating zone 23 betweenplates 49 'and 51, which are separated by i/li; inch from each other,after having been inserted through the inwardly-tapering slot 17 intooperative position within the jacket. The yarns are heated by radiationfrom the brass plates 49, 51 and by the hot air between them. The slotis narrowed to inch by means of blocks of solid insulating material 55,57. Brass plates @i9 and 51 are connected by a brass strip 59 on theside furthest from the slot.

It is regarded as being most important, for the maintenance of uniformtemperature conditions throughout each zone, that heat losses, ormal-distribution, due to convection shall be minimized by good thermalinsulation and by efcient distribution of heat throughout each zone. Thethermal insulation is dependent, for one thing,

on the width of the threading slot 17 and on the insulating efliciencyof the means 7 adopted to block the slot when the yarns are in operativeposition.

As can readily be understood by persons skilled in the art, the loss ofheat by convection will not be so injurious when the heater is mountedhorizontally as when it is mounted vertically, as in the former instancea temperature gradient will be established across the vertical diameterof the heater cross-section, i.e. at right angles to the yarn path,whereas in the latter instance, the temperature gradient will be in thedirection of the yarn path. In the former instance, the temperature inthe heater along the yarn path will be substantially constant; in thelatter instance, not. In fact, the difference in temperature between thetop and bottom of a vertically-mounted heater having a threading slot1A: inch wide and no closure therefor may well be as great as 50%, i.e.the temperature at the bottom of the heater will be 50% less than thedesired equilibrium temperature. If this is the case, of course, theheat treatment required, e.g. setting of the twist in a yarn, will notbe carried out efficiently, if at all.

Eicient thermal insulation of the space containing the heating elementsis necessary in the case of verticallymounted heaters for the additionalreason that convection effects of the ambient atmosphere on the outsideof the heater would otherwise tend to be reproduced in the heaterelements themselves, also, and thus bring about a temperature gradientalong the yarn path.

Accordingly, the threading slot of the heater has to be of very smallwidth and the space surrounding the heating elements has to be lagged soas substantially to prevent the passage of heat to the exterior of theheater' which is in contact with the ambient atmosphere.

Preferably the equilibrium zone heating elements them-v selves, betweenwhich the yarn passes, are also narrowly spaced.

When, as shown, two or more yarns are passed simultaneously through theheater of the invention it is desirable to so guide them into, and holdthem in place within, the heater that the yarns are disposed from oneanotherY within the plane of the gap between the equilibrium heatingelements, in order to avoid more than glancing contact of any of theyarns with either of the surfaces of they elements.

ln addition, the temperature of a zone of the yarnl heater in thevicinity of the yarn path is maintained at a` substantially uniformvalue throughout the Zone, by the arrangement whereby the heaterelements are in heat-con-V ductive contact throughout all or part oftheir length with massive heat-conducting material, such as the brass inthe form of blocks shaped to encompass or lie in contact with the saidheater elements, as described with reference to the illustrativeapparatus.

The massive heat-conducting material ensures that heat is rapidlyconducted in the length direction of the heater; and, when such heateris mounted vertically, the effect of this continuous supply of heat byconduction to all parts of each zone of the heater, is great enoughsubstantially to counteract the effect of the continuous loss of heatdue to convection upwards along the yarn space of theA heater.

Naturally, the form of the massive heat-conducting material will dependon the size and shape of the electric heating elements required to beused in conjunction with it. The elements may be either incorporatedwithin the heat-conducting material, or as shown, `attached orpositioned in heat-conductive contact with the surface of the saidmaterial. In a vertically-mounted heater, as an aid to raising thetemperature of the bottom of the heater, or a zone of the heater, to thedesired temperature, the electric heating elements may have theirheating effect reinforced at the bottom part by the addition of furtherresistance wires, or by the shaping of the elements themselves in such away as to give additional heat in that part. For example, the elements,as in the form illustrated, are shaped like a J; or, when in coil form,the coils may be more closely spaced at the bottom than elsewhere alongthe length of the elements. `In these circumstances, it may besufficient if the massive heat-conducting material incorporates or isattached to that part of the heating element where the heating effect isreinforced.

As has been referred to above, heating apparatus of the kind underconsideration finds a useful application in processes for crimpingrunning yarns by setting false twist which has been inserted in them.The specification of our U.S. application Serial No. 595,543, now PatentNo. 2,93 6,567 describes, inter alia, such a process wherein `a rotatingtwist tube having, for example, a rubber lining or bush, inserts falsetwist in a yarn or yarns led through the tube and in contact with thebush on one side of the axis thereof, and the successive twistedportions of the yarn are led through a heater to set the twist therein.The present apparatus is very suitable for achieving such twist-settingin this crimping process. In one example of the use of such apparatus,denier multifilament polyhexamethylene adipamide yarn was led through atwisttube such as is described in the specification of the aforesaidU.S. application Serial No. 595,543, now Patent No. 2,936,567 to insertfalse twist therein, the yarn being heated in the highly twistedcondition by passage through apparatus according to the presentinvention. Under the conditions of twist inserted in the yarn, thevirtual denier of the yarn in the apparatus was approximately 150 andits linear speed owing to the amount of contraction occurring, 250 feetper minute, when the yarn was Wound up at 370 -feet per minute. In theform of apparatus used, the first zone, of 4- inches length, was heatedby an electrical resistance wire to 680 C. (this being the temperatureattained by a thermocouple allowed -to reach equilibrium in the air inthe middle of the zone). The second Zone, of 14 inches length, washeated to 250 C. The crimped yarn so set by the illustrative apparatusWas of comparable quality to yarn produced under similar conditions butusing a 3 foot elliptical reflector heater at a temperature of 380 C.(this heater having a comparable total power consumption).

In a two-zone heater of the type actually illustrated, which was used ina similar process for false-twist crimping 60 denier or 70 deniermu-ltilament yarns of polyhexamethylene adipamide, the two Zones of theheater were at 460 C. `and 260 C. respectively, with the yarns beingwound up at 380 feet/minute (or 370 feet/minute for the 70 denieryarns). The lengths of the two zones were 7% inches and; 14 inchesrespectively.

It will, of course, be realised that whilst the apparatus as abovedescribed, brings about setting of yarn in a dry atmosphere it ispossible to inject steam into one or both zones so that the setting iscarried out in a humid atmosphere. Equally, the atmosphere within theapparatus may be another inert gas rather than air or steam,Furthermore, the cross-section of the apparatus need not, of course, bebox-like, but may be circular or elliptical.

I claim:

1. Apparatus lfor the heat treatment of running yarns passedtherethrough comprising: an elongated thermally insulated heating jacketdefining within its interior at least one heating zone; said jackethaving a threading slot extending longitudinally over one side andcommunicating with said zone, the slot being of inwardly tapered crosssection; insulating block means disposed partially across said slot intransverse relationship adjacent to the inner end thereof; heatconducting material disposed within said zone and of a configuration toprovide a passage for the yarn; heating means in contact with said heatconducting material; a thermally insulated closure member which iscomplementary in shape to said slot, said member being adapted forabutting engagement with the adjacent lateral surface of said slot whenin a closed position in the apparatus while the inner surface thereof isspaced from the outside surface of Said insulating block means when inthe closed position to provide an air gap therebetween, whereby aleakage path is provided during operation of the apparatus.

2. Apparatus dened in claim 1 wherein said air gap is a maximum ofapproximately lAz".

References Cited in the file of this patent UNITED STATES PATENTS1,266,735 White May 21, 1918 2,204,603 Kline et al. June 18, 19402,211,141 Lobasso Aug, 13, 1940 2,343,351 Wedler Mar, 7, 1944 2,345,541Scholze Mar. 28, 1944 2,688,067 Sonnino et al. Aug. 31, 1954 2,820,280Benn Jan. 21, 1958 2,846,752 Lessig Aug. 12, 1958 2,888,733 Wegener.Tune 2, 1959 2,958,921 Gilchrist Nov. 8, 1960 FOREIGN PATENTS 546,015Italy July 11, 1956 773,816 Great Britain May 1, 1957

